Shear line, northeast monsoon, and easterlies to batter Luzon, Visayas, Mindanao

The Philippines is set to experience a turbulent weather pattern as the shear line, northeast monsoon, and easterlies converge, bringing widespread rains, thunderstorms, and the risk of flash floods across Luzon, Visayas, and Mindanao. The Philippine Atmospheric, Geophysical, and Astronomical Services Administration (PAGASA) issued a severe weather alert on January 29, 2025, warning residents to prepare for possible landslides and flooding due to intense rainfall.

The combination of these three weather systems is expected to create challenging conditions, particularly in low-lying and coastal areas. Authorities are urging communities to stay vigilant and take necessary precautions as the inclement weather persists.

Shear line triggers heavy rain and landslide risks in Visayas, Bicol, and Southern Luzon

The shear line, a boundary where cold and warm air masses meet, is currently affecting the Visayas and the eastern section of Southern Luzon. This phenomenon is causing cloudy skies with scattered rains and isolated thunderstorms, with moderate to heavy rainfall expected at times.

According to PAGASA, the affected areas include:

• Visayas
• Bicol Region
• Quezon
• Oriental Mindoro
• Marinduque
• Romblon
• Dinagat Islands
• Surigao del Norte

The primary concern is flash floods and landslides, as continuous rainfall could lead to water saturation in vulnerable slopes and river basins. PAGASA advises residents in landslide-prone areas to remain alert and prepare for possible evacuations.

“The combination of the shear line’s instability and the existing saturated soil in these areas increases the likelihood of floods and landslides,” PAGASA stated.

Northeast monsoon brings persistent rains to Cagayan Valley, Cordillera, and Aurora

Meanwhile, the northeast monsoon, locally known as Amihan, is bringing overcast skies and steady rains across Cagayan Valley, Cordillera Administrative Region, and Aurora. Although the rainfall is expected to be moderate to heavy at times, the impact is generally less severe than that of the shear line.

PAGASA warned that flash floods and landslides could still occur, especially in areas with high terrain and poor drainage. The monsoon is also expected to cause isolated light rains over Metro Manila and the rest of Luzon, though no significant impact is anticipated in these areas.

Easterlies drive thunderstorms across Mindanao

In Mindanao, the easterlies—warm, moist winds from the Pacific—are triggering scattered rains and thunderstorms. Affected regions include:

• Northern Mindanao
• Davao Region
• Caraga

While these weather disturbances are typical during this season, localized thunderstorms can still bring heavy rainfall in short bursts, leading to sudden flooding in urban areas. Residents are advised to monitor weather updates, especially those in flood-prone cities and towns.

For the rest of Mindanao, partly cloudy to cloudy skies with isolated rain showers and thunderstorms are expected. However, PAGASA warns that during severe thunderstorms, flash floods and landslides remain a possibility.

Coastal waters at risk: Strong winds and rough seas expected

Aside from the heavy rains, strong to gale-force winds are expected to impact the country’s eastern coastlines. The northeast monsoon is whipping up rough to very rough coastal waters in the following areas:

• Northern Luzon
• Eastern sections of Central and Southern Luzon
• Visayas

Wave heights in these areas are expected to reach 2.8 to 4.5 meters, making sea travel hazardous. Fishermen and small boat operators are strongly advised to avoid venturing out to sea, as rough waves could capsize smaller vessels.

Meanwhile, the eastern section of Mindanao and the rest of Luzon will experience moderate to strong winds, with waves between 1.5 to 4.0 meters high. The rest of the country will have light to moderate winds and slightly calmer waters, ranging from 0.6 to 2.1 meters in wave height.

Temperature and humidity updates

For those tracking temperature changes, PAGASA reported the following extremes in Metro Manila over the past 24 hours:

• Minimum temperature: 21.9°C (recorded at 1:40 AM)
• Maximum temperature: 29.4°C (recorded at 3:10 PM)
• Minimum relative humidity: 57% (recorded at 3:10 PM)
• Maximum relative humidity: 88% (recorded at 2:00 AM)

Tides and astronomical data

For those in Metro Manila, the tidal forecast for January 30, 2025, is as follows:

• Low tide: 6:26 AM (-0.33 meters)
• High tide: 10:33 PM (1.26 meters)

Astronomical events:

• Sunrise: 6:25 AM
• Sunset: 5:54 PM
• Moonrise: 6:58 AM
• Moonset: 6:43 PM
• Illumination: 1% (waning crescent)

Safety precautions and government response

As the Philippines braces for this turbulent weather, government agencies and local disaster units have been placed on high alert. The National Disaster Risk Reduction and Management Council (NDRRMC) has instructed local government units (LGUs) in high-risk areas to prepare emergency response measures and ensure evacuation centers are ready if needed.

Residents are advised to:

• Stay updated on weather advisories through PAGASA’s official channels.
• Prepare emergency kits with essential supplies, including food, water, and medication.
• Avoid crossing swollen rivers or flood-prone areas to prevent accidents.
• Secure belongings and reinforce homes, especially in coastal areas with expected strong winds.
• Follow LGU instructions regarding evacuation or safety protocols.

Conclusion

The convergence of the shear line, northeast monsoon, and easterlies is creating a high-risk weather scenario for multiple regions in the Philippines. While some areas will experience moderate, persistent rains, others will face intense downpours, strong winds, and coastal hazards.

Authorities are urging residents in Visayas, Southern Luzon, Bicol, and Mindanao to take precautionary measuresagainst flooding and landslides. Meanwhile, fishermen and small boat operators in affected coastal regions are advised to remain onshore until conditions improve.

As the country faces yet another bout of unpredictable weather, vigilance and preparedness remain key in preventing casualties and ensuring the safety of communities. PAGASA continues to monitor developments and will issue further advisories as needed.

For real-time weather updates, residents can visit pagasa.dost.gov.ph or contact the PAGASA Weather Division at (02) 927-1335 or (02) 926-4258.